深入了解Java核心类库--Math类

 public static long round(double a) { long longBits = Double.doubleToRawLongBits(a); long biasedExp = (longBits & DoubleConsts.EXP_BIT_MASK) >> (DoubleConsts.SIGNIFICAND_WIDTH - 1); long shift = (DoubleConsts.SIGNIFICAND_WIDTH - 2 + DoubleConsts.EXP_BIAS) - biasedExp; if ((shift & -64) == 0) { // shift >= 0 && shift <64>> shift) evaluates to floor(a * 2) // ((r >> shift) + 1) evaluates to floor((a + 1/2) * 2) // (((r >> shift) + 1) >> 1) evaluates to floor(a + 1/2) return ((r >> shift) + 1) >> 1; } else { // a is either // - a finite number with abs(a) = 1 and hence a is a mathematical integer // - an infinity or NaN return (long) a; } } public static int max(int a, int b) { return (a >= b) ? a : b; } public static int min(int a, int b) { return (a <= b) ? a : b; } public static int abs(int a) { return (a <0) ? -a : a; } 

 public class Test { public static void main(String[] args) { System.out.println("≥3.2的最小整数为："+Math.ceil(3.2));//output:4 System.out.println("≤3.2的最大整数为："+Math.floor(3.2));//output:3 System.out.println("3.2四舍五入为："+Math.round(3.2));//output:3 System.out.println("-1,5中较大的数为："+Math.max(-1,5));//output:5 System.out.println("-1,5中较小的数为："+Math.min(-1,5));//output:-1 System.out.println("随机产生[0,5)范围的数"+Math.random()*5);//output:[0,5)中任意的随机数 System.out.println("25的平方根为："+Math.sqrt(25));//output:5 System.out.println("-9的绝对值为："+Math.abs(-9));//output:9 System.out.println("2^3的值为："+Math.pow(2,3));//output:8 System.out.println("以e为基数的对数为："+Math.log(10)); System.out.println("以10为基数的对数为："+Math.log10(100));//output:2 } }